Absorption refrigeration system

ABSTRACT

An absorption refrigeration system employing a pair of staged air-cooled absorbers and a pair of staged adiabatic evaporators. Strong solution from the generator passes first to the lowpressure absorber from which it flows through the high-pressure absorber back to the generator. Refrigerant liquid is flashcooled in the high-temperature adiabatic evaporator stage from which it passes to the low-temperature adiabatic evaporator for further flash-cooling and from which it is passed through a refrigerant heat exchanger for cooling a refrigeration load and back to the high-temperature adiabatic evaporator. The system further embodies a scoop pump for circulating solution to and from the absorber and generator which includes a hermetic housing formed with an annular embossment and mounting therewithin a rotatable trough provided with an annular flange which cooperates with the embossment to provide a hydrodynamic seal dividing the interior of the housing into high-pressure and low-pressure zones.

United States Patent [72] lnventor LoulsII.Leonard,Jr.

Dewitt,N.Y. 211 AppLNo. 20,771

[22] Filed [45] Patented [7 3 Assignee Mar. 18, 1970 Nov. 30, 1971Carrier Corporation Syracuse, NY.

[54] ABSORPTION REFRIGERATION SYSTEM 4 Claims, 2 Drawing Figs.

[52] U.S. Cl 62/476, 277/13, 415/89 [5 1] Int. Cl F25b 15/06 [50] Fieldof Search. 62/476;

Primary Examiner-William F. ODea Assistant Examiner-P. D. FergusonAttorneys-Harry G. Martin, Jr. and J. Raymond Curtin ABSTRACT: Anabsorption refrigeration system employing a pair of staged air-cooledabsorbers and a pair of staged adiabatic evaporators. Strong solutionfrom the generator passes first to the low-pressure absorber from whichit flows through the high-pressure absorber back to the generator.Refrigerant liquid is flash-cooled in the high-temperature adiabaticevaporator stage from which it passes to the lowtemperature adiabaticevaporator for further flash-cooling and from which it is passed througha refrigerant heat exchanger for cooling a refrigeration load and backto the high-temperature adiabatic evaporator. The system furtherembodies a scoop pump for circulating solution to and from the absorberand generator which includes a hermetic housing formed with an annularembossment and mounting therewithin a rotatable trough provided with anannular flange which cooperates with the embossment to provide ahydrodynamic seal dividing the interior of the housing intohigh-pressure and low-pressure zones.

PATENTEIJuuv 30 l97| 3, 624, 705

QUNVENTOR.

ATTORNEY 42 LOUIS H. LEONARD, JR.

ABSORPTION REFRIGERATION SYSTEM BACKGROUND OF THE INVENTION Thisinvention relates to absorption refrigeration systems and to pumps usedtherein. It is known to employ separate centrifugal pumps to circulatestrong absorbent solution to an absorber and to also circulate weakabsorbent solution from the absorber through a solution heat exchangerto the generator. It has also been proposed to circulate absorbentsolution in an absorption refrigeration system by using one or morescoop pumps generally taking the form of a closed chamber within whichis rotatably mounted a rotatable pan for centrifugally impelling liquiddirected into the chamber through an inlet conduit. The liquid is pickedup by a scoop or eduction tube disposed in the pan. Scoop pumps haveamong their advantages simplicity of construction and will not cavitatesignificantly even through a relatively small quantity of fluid is fedto them. Further, scoop pumps have other advantages, such as eliminationof the requirement for suction head, the ability to pump mixtures ofnoncondensables and liquids, and can be run with no liquid therein ifrequired, without deleterious results.

It is desirable for reasons of simplicity of construction that theinterior of the scoop pump housing be constructed to essentially balancethe pressure difference between the absorber and generator so that asingle pump having a plurality of pans can be used to satisfy all thepump requirements of the system. Mechanical seals are subject to wearand leakage and can prove troublesome to keep in alignment. They mayalso impose excessive friction forces which increase cost and decreaseefficiency of the pump. Consequently, a need exists for seal means ofrelatively simple and yet highly reliable construction for dividing thepump housing interior into what may be termed relatively highandrelatively low-pressure zones.

SUMMARY OF THE INVENTION In accordance with this invention, there isprovided an aircooled absorption refrigeration machine which may be ofthe type having single or multiple evaporator and absorber stages.

The solution is passed between the absorber and generator by the fluidtransfer apparatus, preferably taking the form of a stationary housingmember mounting therewithin a plurality of scoop pumps. The pumpsinclude a plurality of rotatable pan members. One of the members isprovided with an annular flange received in an annular liquid-filledtrough formed on the other member to provide a rotating hydrodynamicseal which balances the pressure difference between the absorber andgenerator or between other different pressure locations in the system atwhich the pump may be required to operate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic flow diagram,partially in cross section, of an absorption refrigeration machineembodying a fluid transfer apparatus in accordance with this invention;and

FIG. 2 is a fragmentary cross-sectional view illustrating a modifiedpump seal arrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with a preferredembodiment of this invention, there is provided an absorptionrefrigeration system which utilizes water as a refrigerant and anaqueous solution of lithium bromide as an absorbent. A suitableadditive, such as octyl alcohol (2-ethyl-n-hexanol) for heat transferpromotion and suitable corrosion inhibitors may be added to thesolution. Strong solution" as referred to herein, is a concentratedsolution of lithium bromide, which is strong in absorbing power, andweak solution lithium bromide which is weak in absorbing power.Intermediate solution" refers to solution intermedient in absorbingpower and concentration between strong and weak solutions,

Referring to the drawing, there is shown an absorption refrigerationsystem comprising a generator 10, a refrigerant condenser 11, ahigh-temperature adiabatic evaporator [2, a low-temperature adiabaticevaporator 13, a high-pressure absorber 14, a low-pressure absorber 15,a sensible refrigerant heat exchanger 16, an absorbent solution heatexchanger 17, and solution transfer apparatus A connected to providerefrigeration. A purge unit 18 may be employed to remove relativelynoncondensable vapors from the system from any convenient location.

Generator 10 comprises a boiler preferably having a shell 25, aplurality of internal flue tubes 26, a heat source such as gas burner27, and a flue gas collector 28. Weak absorbent solution enters thegenerator and is boiled therein to concentrate the absorbent solution byvaporizing refrigerant. The concentrated or strong solution isdischarged from the generator through strong solution passage 30. Othertypes of wellknown boilers or generators employing either a combustiblefuel, or a heating fluid, such as steam or water, may be employed forconcentrating the absorbent solution.

The strong solution leaving the generator is preferably cooled bypassing through the shell side passage of solution heat exchanger 17. Inthe preferred embodiment, fluid.

transfer apparatus A is employed to pass the strong solution from heatexchanger 17 to the low-pressure absorber.

Low-pressure absorber 15 preferably comprises a plurality of verticallydisposed finned absorber tubes 36, opening at their upper ends into alow-pressure vapor header 35. Strong solution is discharged fromstrong-solution passage 136 into vapor header 35 of low-pressureabsorber 15. The lower ends of absorber tubes 36 open into alow-pressure liquid header 38. A fan 39 is preferably disposed adjacentabsorber tubes 36 for passing ambient cooling air over the exteriorsurfaces of the absorber tubes of both the high and low-pressureabsorbers to cool absorbent solution passing down through the tubes.While the preferred embodiment of this invention is directed to anair-cooled absorption refrigeration system, a liquid-cooled absorberemploying cooling 'tower water for cooling the absorbent solution, maybe used instead of the aircooled arrangement illustrated.

The upper ends of absorber tubes 36 are shown projecting upwardly intovapor header 35 to form a weir for distributing the strong solution ontothe interior walls of the absorber tubes. The strong solution passesdownwardly through absorber tubes while being cooled by ambient airpassing over the exterior surfaces of the tubes, thereby maintaining alow solution vapor pressure or saturation temperature. Refrigerant vaporfrom low-temperature evaporator 13 enters the ends of absorber tubes 36from vapor header 35 and passes downwardly therein, concurrently withthe strong solution. This refrigerant vapor contacts the strongabsorbent solution within absorber tubes 36, and is absorbed therein,thereby forming absorbent solution of intermediate strength.

The intermediate solution is collected in liquid header 38 from which itpasses through a siphon tube 40 having an upwardly arched portion 41 anda downwardly extending leg 42. The upwardly arched portion 41 of siphontube 40 opens into liquid header 38 and the downwardly extending leg 42opens into conduit 45 leading to the solution transfer apparatus.

Highpressure absorber 14 is similarly provided with a plurality ofvertically disposed finned absorber tubes 46 having their upper endsopening into a high-pressure vapor header 47 to establish a level ofintermediate strength absorbent solution therein. The lower ends of thehigh-pressure absorber tubes 46 open into high-pressure liquid header48. Intermediate strength absorbent solution from liquid header 47together with refrigerant vapor from high-temperature evaporator 12flows downwardly through absorber tubes 46 while the absorbent solutionis cooled therein by fan 39 passing ambient air over the exteriorsurfaces of the absorber tubes.

The absorption of refrigerant vapor into the intermediate solutionpassing downwardly through absorber tubes 46 dilutes the intermediatesolution and the resulting weak solution is collected in liquid header48. Weak solution passes out of liquid header 48 through siphon tube 50having an upwardly arched portion 51 and a downwardly extending leg 52,which forms a liquid seal to prevent escape of some of the refrigerantvapor from the high-pressure absorber. Weak solution passes from siphontube 50 into weak-solution reservoir 61. Weak solution from reservoir 61passes through passage 138 and is forwarded by solution transferapparatus A through weak-solution passage 140 and the interior passageof solution neat exchanger 17 through passage 63 to generator forreconcentration.

The refrigerant vapor formed by boiling weak solution passes out of thegenerator through refrigerant vapor line 65 into vapor header 70 ofrefrigerant condenser 11. Refrigerant condenser 11 preferably comprisesa plurality of vertically disposed finned condenser tubes 71 openingupwardly into vapor header 70 and downwardly into liquid header 72.Cooling air is passed over the exterior surfaces of finned tubes 71 by asuitable fan such as fan 39. The refrigerant vapor is condensed withincondenser tubes 71 by heat exchange with the air and the condensedrefrigerant passes through the refrigerant liquid line 74 into thehigh-temperature refrigerant evaporator 12.

High-temperature adiabatic evaporator 12 may comprise a shell 80 fromwhich a refrigerant vapor passage 86 extends to vapor header 47 of thehigh-pressure absorber. The warm refrigerant, upon enteringhigh-temperature evaporator 12, is adiabatically flash-cooled to thecorresponding absorber pres sure and saturation temperature. Theunevaporated major portion of liquid refrigerant in adiabatic evaporator12 is cooled due to flashing of a portion of the refrigerant therein.

The cooled refrigerant liquid reaching the bottom of thehigh-temperature adiabatic evaporator is discharged by gravity throughcool refrigerant line 85, having a liquid trap 87, into low-temperatureadiabatic refrigerant evaporator 13. Trap 87 provides a liquid sealbetween the high-temperature and low-temperature adiabatic evaporatorsto prevent the passage of a substantial quantity of vapor between themand to maintain the pressure difference between the evaporator stages.

The cooled refrigerant discharge from the high-temperature adiabaticevaporator 12 into the low-temperature adiabatic evaporator 13 is againadiabatically flash-cooled to a still lower temperature. The coldrefrigerant liquid reaching the bottom of low-temperature adiabaticevaporator 13 is discharged by gravity flow through cold refrigerantliquid passage 95 into a suitable refrigerant reservoir 96, which isvertically below and may be integrally formed with the lowtemperatureevaporator.

The cold-liquid refrigerant is then pumped by a refrigerant pump 97 inrefrigerant liquid line 98 through refrigerant heat exchanger 16.Refrigerant heat exchanger 16 comprises a sensible heat exchanger forcooling the desired refrigeration load, which, in the illustratedembodiment, is air passing by means of fan 103 through duct 104 insensible heat exchange relation with the refrigerant passing throughrefrigerant heat exchanger 16. The warmed liquid refrigerant, havingabsorbed heat from the refrigeration load, returns to thehigh-temperature evaporator through refrigerant line 105.

Fluid transfer apparatus A of this invention comprises a stationaryhermetic housing 110 formed on its circumference with an annularembossment 111 defining interiorly of the housing a circumferentiallyextending, radially inwardly opening, concave groove or trough 112.Within the housing 110 there is mounted scoop pump means comprising acentral partition member 113 mounted by means of a collar member 114upon cylindrical shaft 115 forming an outer shell of drive means 116.Shaft 115 is journaled in bearing means 117 and 118, and interiorly ofthe housing 115 is a pair of axially spaced magnets 119 and 120, themagnet 119 being connected to shaft means 121 driven by motor means 122.

The central partition member 113 has secured thereto an annular flange123 having a pair of radially inwardly directed flange sections 124 and125. Radially inwardly spaced from the annular member 123 is an annularwall member 126 having a radially inwardly directed flange section 127attached thereto. Annular wall member 123 is spaced radially inwardly ofthe outer circumference of the partition member 113 so as to provideprotruding annular flange or wall portion 128 received in the annularcavity or groove 112 to define therewith a rotating hydrodynamic seal.The annular wall member 123 and the radially inwardly directed wallsections define with the central partition 113 and housing interior apair of scoop pump pans forming chambers C-1 and C2, while the annularwall member 126 and its radially inwardly directed flange portion 127,in cooperation with the central partition 113 and housing interior,define a third scoop pump pan forming solution circulation chamber C3.

The solution circulation chamber Cl receives therein discharge nozzle130 of conduit means 45 leading from liquid header 38 of low-pressureabsorber 15 for transferring to the compartment Cl solution ofintermediate concentration. Leading into this same chamber is eductionorifice 131 of conduit means 132 which functions to pump intermediatesolution to high pressure absorber 14.

The chamber C3 has disposed therein discharge nozzle 133 of conduitmeans 134 communicating through solution heat exchanger 17 with conduit30 to feed to chamber C3 strong solution from generator 10. Chamber C3also has disposed therein eduction orifice 135 of conduit means 136 fortransferring to low-pressure absorber 15 strong solution from chamberC3.

Solution circulation chamber C2 receives therein discharge nozzle 137 ofconduit means 138 which communicates with reservoir 61 to drain intochamber C2 weak solution which is pumped therefrom by eduction orifice139 of conduit means 140 communicating through solution heat exchanger17 and conduit 63 to transfer to generator 10 weak absorbent solutionfor reconcentration therein.

Chamber C-l also has disposed therein inlet orifice 141 of pickup scoop142 functioning to transfer to this chamber liquid which splashes intothe bottom of housing 110 during operation or which drains into thebottom of the housing 110 upon machine shutdown.

The flange portion 128 on the central partition 113, in cooperation withthe embossment 111 on the housing 110, divides the interior of thehousing into a relatively low-pressure zone in chamber C2 and arelatively high-pressure zone in chambers C1 and C3. These pressures arebalanced by the difference in height of the liquid in the rotatinghydrodynamic seal provided by this invention because the sides of trough112 overlap flange 128 a substantial extent. It is to be seen thatconduit 134 has a restriction 143 therein and that conduit 45 is alsoprovided with a restriction 144. Strong solution draining into chamberC3 through conduit 134 from generator 10 flash-cools down to absorbervapor pressure by reason of being exposed to intermediate concentrationsolution in chamber Cl.

FIG. 2 illustrates another type of hydrodynamic seal which can beutilized in accordance with this invention to provide a relativelyfrictionless liquid seal between radially spaced chambers C1 and C3. Inthis embodiment, pump housing member 210 is provided with a radiallyoutwardly extending flange member 211, and rotatable wall 213 isprovided with a radially inwardly opening trough 227 into which flange211 extends. Trough 227 is secured with and forms a part of pan member226 and flange 211 is secured with and forms a part of housing member210. When pan member 226 is rotated, liquid in trough 227 assumes aheight on either side of flange 211 sufiicient to balance the differencein pressure between chambers 0-1 and C3.

The arrangement described is particularly advantageous because aneffective seal is provided without the necessity of maintaining aprecise alignment between the rotating and stationary parts and which iscapable of providing effective sealing even through clearances maychange due to bearing wear. Furthermore, the seal provided is relativelyfriction free, automatically compensates for differences in pressure andunlike mechanical seals is not subject to wear. Since the liquid in theseal is essentially a rotating liquid annulus, whether the trough bestationary or rotating, there is a centrifugal component of force actingon the liquid which permits a given pressure difference to be balancedby a relatively small difference in height of the liquid column oneither side of the flange member. Furthermore, on machine shutdown, theseal may be broken and the liquids are enabled to intermix in the bottomof the housing to form an antifreeze mixture having a relatively lowsolidification temperature. The apparatus may also be utilized in eithera vertical or horizontal axial plane by suitable design.

Various other modifications may bemade within the scope of the followingclaims.

lclaim:

1. An absorption refrigeration system comprising a generator forconcentrating absorbent solution by vaporizing refrigerant therefrom toform strong absorbent solution; a condenser connected for condensingrefrigerant vapor formed in said generator; an evaporator forevaporating the refrigerant liquid therein; and absorber connected tothe evaporator for absorbing refrigerant vapor formed therein; and afluid transfer apparatus comprising; a stationary hermetic housingmember; a first scoop pump in said housing member comprising a rotatablepan member, a first inlet passage disposed for supplying liquid to saidpan member and a first eduction conduit having an eduction orificedisposed in said pan; a second scoop pump in said housing comprisinganother rotatable pan member, a second inlet conduit disposed forsupplying liquid to said other pan and a second eduction conduit havingan eduction orifice disposed in said other pan; and a liquid sealbetween said first and second scoop pumps, said seal comprising anannular trough adapted to contain liquid secured with a first one ofsaid members and an annular flange secured with a second one of saidmembers extending into said trough to contact liquid therein, said firstand second members being rotated relative to each other when said panmembers are rotated, said liquid serving to inhibit the passage of vaporfrom one pan of said scoop pump to the other pan thereof during relativerotation of said first and second members.

2. An absorption refrigeration system as defined in claim 1 wherein saidtrough comprises an annular, radially inwardly open groove in saidhousing member, said flange extending radially outwardly from at leastone of said pans into said trough to form a liquid seal therewith whensaid trough contains liquid.

3. An absorption refrigeration system as defined in claim 1 wherein thefirst scoop pump is exposed to absorber pressure and the second scooppump is exposed to generator pressure, said seal having a radialdimension sufficient to balance the difi'erence in pressure between saidpans with a column of liquid in said trough on one side of said flange.

4. An absorption refrigeration system as defined in claim 1 wherein saidtrough comprises an annular radially inwardly open portion of one ofsaid pan members, and said flange extends radially outwardly from saidhousing into said trough to form a liquid seal with the liquid in saidpan when said trough contains liquid during operation of said fluidtransfer apparatus.

i i i i i

1. An absorption refrigeration system comprising a generator for concentrating absorbent solution by vaporizing refrigerant therefrom to form strong absorbent solution; a condenser connected for condensing refrigerant vapor formed in said generator; an evaporator for evaporating the refrigerant liquid therein; and absorber connected to the evaporator for absorbing refrigerant vapor formed therein; and a fluid transfer apparatus comprising: a stationary hermetic housing member; a first scoop pump in said housing member comprising a rotatable pan member, a first inlet passage disposed for supplying liquid to said pan member and a first eduction conduit having an eduction orifice disposed in said pan; a second scoop pump in said housing comprising another rotatable pan member, a second inlet conduit disposed for supplying liquid to said other pan and a second eduction conduit having an eduction orifice disposed in said other pan; and a liquid seal between said first and second scoop pumps, said seal comprising an annular trough adapted to contain liquid secured with a first oNe of said members and an annular flange secured with a second one of said members extending into said trough to contact liquid therein, said first and second members being rotated relative to each other when said pan members are rotated, said liquid serving to inhibit the passage of vapor from one pan of said scoop pump to the other pan thereof during relative rotation of said first and second members.
 2. An absorption refrigeration system as defined in claim 1 wherein said trough comprises an annular, radially inwardly open groove in said housing member, said flange extending radially outwardly from at least one of said pans into said trough to form a liquid seal therewith when said trough contains liquid.
 3. An absorption refrigeration system as defined in claim 1 wherein the first scoop pump is exposed to absorber pressure and the second scoop pump is exposed to generator pressure, said seal having a radial dimension sufficient to balance the difference in pressure between said pans with a column of liquid in said trough on one side of said flange.
 4. An absorption refrigeration system as defined in claim 1 wherein said trough comprises an annular radially inwardly open portion of one of said pan members, and said flange extends radially outwardly from said housing into said trough to form a liquid seal with the liquid in said pan when said trough contains liquid during operation of said fluid transfer apparatus. 